Conventional devices for delivering therapeutic energy to tissue include a handle and a probe coupled to the handle. The probe contains at least one electrode to which an electrical power source is coupled. The power source allows the electrode to deliver the therapeutic energy to a targeted tissue, thereby causing ablation of the tissue.
In certain applications, it is desirable to provide a probe having a relatively small cross-section, for example 1 cm in diameter or less, wherein the electrodes are moved to a compact state to a configuration where the distance between the distal section of any two electrodes is smallest, so as to be placeable within a position inside of the outermost dimension of the probe. Prior art devices have utilized flexible materials having shape memory (such as nickel titanium, also known as “Nitinol”) for the electrodes in order to accomplish this. However as the distal sections of the electrodes are moved from a compact position to a more expanded position where the distance between at least distal sections of two electrodes becomes greater, it is difficult to keep such electrodes in proper alignment if they are composed of flexible materials. Further, it is often difficult or sometimes not possible to place the electrodes in the correct location of the tissue to be ablated.
Applications of a probe that could be utilized as described ideally would involve the emerging technology of Irreversible Electroporation (IRE). Irreversible electroporation (IRE) involves the use of electrical pulses to target tumor tissue in the range of microseconds to milliseconds that can lead to non-thermally produced defects in the cell membrane that are nanoscale in size. These defects can lead to a disruption of homeostasis of the cell membrane, thereby causing irreversible cell membrane permeabilization which induces cell necrosis, without raising the temperature of the tumor ablation zone. During IRE ablation, connective tissue and scaffolding structures are spared, thus allowing the surrounding bile ducts, blood vessels, and connective tissue to remain intact. With nonthermal IRE (hereinafter also called non-thermal IRE), cell death is mediated through a nonthermal mechanism, so the heat sink problem associated with many ablation techniques is nullified. Therefore the advantages of IRE to allow focused treatment with tissue sparing and without thermal effects can be used effectively in conjunction with thermal treatment such as RF that has been proven effective to prevent track seeding; this will also allow (in this example embodiment) the user to utilize determined RF levels (or long-DC pulses) leading to in some cases ablation and in some cases coagulation of blood vessels of all sizes encountered during treatment. IRE can be utilized effectively with known techniques of thermal damage including mediating tumor cell death and bringing about coagulation along a tissue track.
Therefore, it would be desirable to provide a device and method which includes electrodes that can be placed within a relatively small diameter by being placed in a compact position to a more expanded position where the distance between at least distal sections of two electrodes becomes greater, and then returned to the compact position while the distal sections of the electrodes remain in parallel with each other. With some therapies, parallel electrodes are needed; parallel embodiments are in certain cases better than curved flexible electrodes such as in use with hard surfaces, tumors, or cancers. Maintaining a parallel orientation can be critical to treatment success. Additionally, this device could be used to mediate irreversible electroporation separately or in conjunction with reversible electroporation, long-DC pulses, and Radio-Frequency (RF) technologies which provides additional advantages of treatment when used in conjunction with features such as the parallel electrode orientation.